1. Technical Field
The invention relates to photonic devices. In particular, the invention relates to photonic devices that use surface plasmons.
2. Description of Related Art
A consistent trend in integrated circuits (ICs) is toward an increase in data rate or equivalently an increase in bandwidth of data channels within the IC. Concomitant with the increased bandwidth is a desire to reduce an overall size of the IC, which typically has included pressure to decrease a size of individual components that make up portions of the IC. Photonics, the use of optical signals for processing and transporting data in ICs, has been developed to facilitate much higher bandwidths than is possible with more conventional, purely electronic ICs. However, photonic components often require considerably larger dimensions or surface real estate on the IC than functionally equivalent electronic components. Relatively recently the use of surface plasmons in place of or in conjunction with conventional optical signals in photonic ICs has attracted a great deal of interest. A surface plasmon at a given frequency generally has a wavelength that is considerably smaller than a wavelength of an optical signal in free space or a dielectric waveguide at the same frequency. As such, photonic components based on surface plasmons may be much smaller than similar purely conventional photonic components.
A principle component of many photonic ICs is a modulator. A modulator is used to vary or modulate an intensity and/or a phase of a signal passing through the modulator. For example, a modulator may be used to impress a data stream onto an optical signal acting as a carrier to facilitate transmitting the data stream from one point to another either within an IC or between ICs or other photonic system elements. Plasmonic modulators based on changing a phase of gallium (Ga) metal used to support propagation of a surface plasmon have been demonstrated. The phase change (e.g., between a solid α-Ga phase and a metallic Ga liquid phase) is induced by changing a temperature of the Ga metal. Another approach is based on modulating guided long range surface plasmon polaritons (LRSPPs) by either heating a polymer dielectric layer to induce loss in the propagating plasmon mode or employing a Mach-Zehnder (MZ) interferometer and using heat via a thermo-optic effect to change a phase length of one arm relative to another arm of the MZ interferometer to affect plasmon modulation.
However, these plasmonic modulators generally cannot achieve sufficient modulation bandwidths to be useful for high bandwidth application (e.g., data rates above 10 GHz). As such, there is considerable interest in providing means for modulating surface plasmons that will facilitate high data rate modulation. Providing such means would satisfy a long felt need.